Lowes or home depot have the perfect solution. Wire that is thick as hell, with a heavy duty insulation. it is less conductors though, where car stereo power wire has thousands of conductors, this wire will have less than 100 thick conductors.
you dont wanna do that man... go to your local car stereo shop, look at the big wire and see how flexible it is, then go to the hardware store and try flexing it. it will be a bia to run that wire in your car, in a house it is a different story.
you can go that route if you want, but trust me, live and learn. there are someways you can save money, and there are some ways you can screw yourself, and sometimes those two comcepts fall under the same category
if you want to then go for it. but the end result is going to be a lumpy wire that going to have sharp defined bends(as opposed to a nice smooth flow), and it is going to look like something that should have been hidden behind a sheet of drywall.
but if you want to use it and save a few bucks, go for it.
The best way to look at power wire is this. Try breathing through a straw, then try breathing through a paper towel roll. If you see the benefit for that, then you will see the benefit for bigger wire. Bigger is not always needed, but it can never be too big...(insert dirty joke here____________). Stay away from anything Home Depot or Lowes or any place like that sells for 12 volt wiring. You would think it would be the same thing, but way different, okay...maybe not WAY.